1. Field of the Invention
Apparatuses consistent with the present invention relate to a liquid crystal display (LCD) apparatus using a light emitting diode (LED) as a light source.
2. Description of the Related Art
A liquid crystal display (LCD) apparatus is a kind of flat panel display (FPD) apparatus, which converts various electric information generating from all sorts of devices into visual information by using a change of transmissivity in a liquid crystal according to a voltage applied thereto and displays it. Contrary to a cathode ray tube (CRT) display apparatus, the FDP apparatus needs a backlight because it does not have a self-luminosity. However, the FDP apparatus consumes little electric power and can be used in a portable type device because it is driven with a low driving voltage. Thus, the FDP apparatus is widely used in a watch, a TV, a monitor for computer, etc.
Such a LCD apparatus usually includes a liquid crystal panel, and a backlight module arranged adjacent to the liquid crystal panel.
The liquid crystal panel is provided with a pair of substrates arranged in a minutely spaced-apart relation to each other, a liquid crystal interposed in a space between the substrates, and a driving circuit to drive the liquid crystal.
According to a method of driving the liquid crystal, the liquid crystal panel is classified into an active matrix type to drive a pixel capacity by using switch elements, a passive matrix type to drive a pixel capacity without using switch elements, etc.
Particularly, the active matrix type liquid crystal panel can be further classified into a type using three terminal type switch elements such as thin film transistors (TFT), a type using two terminal type switch elements such as thin film diodes (TFD), etc.
The backlight module is provided with a light guide plate arranged adjacent to the liquid crystal panel, and a light source to irradiate light to the light guide plate. Light conveyed to the light guide plate from the light source is guided to the liquid crystal panel through a diffusing plate and/or a prism.
A fluorescent lamp, such a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), etc., is usually used as the light source of the backlight module. However, the fluorescent lamp is disadvantageous in that a lifespan is shortened due to a change of gas pressure in plasma, an inverter is required to realize a high driving voltage of several hundred volts necessary for plasma discharge, and a consumption efficiency of electric power is low.
Accordingly, recently a light emitting diode (LED) is in the spotlight as the light source for use in the backlight module. The LED is a light emitting element, which produces light by a light emitting phenomenon generating when a voltage is applied to a semiconductor. The LED is advantageous in that as compared with the conventional light source such as a fluorescent lamp, a size is relatively small, a lifespan is guaranteed for a relatively long time, an energy efficiency is relatively high since an electric energy is directly converted into a light energy, and a relatively low driving voltage is required.
However, when the LED is used as the light source for the backlight module in the LCD apparatus, it is disadvantageous in that due to heat of high temperature generating while the LED is operated, the liquid crystal panel is subject to a negative influence and a light emitting performance of the LED itself is deteriorated. Accordingly, recently, there have been developed and disclosed various types of heat emitting structures, which can effectively emit the heat from the LED.
FIG. 1 is a side section view exemplifying a related art LCD apparatus.
As shown in the drawing, the related art LCD apparatus includes a liquid crystal panel 1, a backlight module 2 to irradiate light to the liquid crystal panel 1, a controller 3 to drive the liquid crystal panel 1 and the backlight module 2, and a frame 4 to which the liquid crystal panel 1 and the backlight module 2 are mounted.
A driving circuit board (not shown) for liquid crystal is connected to the liquid crystal panel 1.
The backlight module 2 includes a LED light source 5. The LED light source 5 is provided with a plurality of LEDs 5a, and a circuit board 5b on which the plurality of LEDs 5a are mounted.
At a rear side of the LED light source 5 is arranged a heat radiating member 7 having a plurality of heat radiating pins 7a. The heat radiating member 7 emits heat generating from the LED light source 5 to the outside.
The controller 3 includes a power supply, an inverter, a main control board, all sorts of electric elements and sensors, etc., which are not shown in the drawing, and controls a whole operation of the LCD apparatus. The frame 4 is provided with a front frame part 4a to which the liquid crystal panel 1 is mounted, and a rear frame 4b arranged behind the front frame part 4a.
Between the frame 4 and the backlight module 2 are arranged a first shield 8 to surround the backlight module 2 and the liquid crystal panel 1, and a second shield 9 to surround the controller 3.
The first and the second shields 8 and 9 are made of an electric-conductive material so as to shield all sorts of electromagnetic waves generating from the backlight module 2 and the controller 3.
However, such a related art LCD apparatus is disadvantageous in that the heat radiating member 7 used for emitting the heat of high temperature generating from the LED light source 5 occupies a large installation space, thereby increasing a size of the LCD apparatus.
Further, the related art LCD apparatus is disadvantageous in that there is no heat radiating structure to emit all sorts of heat of high temperature generating from the controller 3, thereby deteriorating a display quality of the LCD apparatus.
Also, the related art LCD apparatus is disadvantageous in that there is installed a shield structure such as the first and the second shields 8 and 9 to intercept the electromagnetic waves generating from the backlight module 2 and the liquid crystal panel 1, thereby increasing the number of assembling parts and processes and enlarging a volume of the LCD apparatus.